WOOD RESEARCH Volume 62, Number 5, 2017
Igor Čunderlík, Peter Vilkovsky, and Vladimír Račko

Shear strength and analysis of shear area on wood/bark interface on beech wood (Fagus sylvatica L.)

The structure of both cambium and the last-differentiated cells from cambium influence the adhesion of bark on wood. In the submitted paper, the bark/wood adhesion is evaluated by means of measuring the shear strength in longitudinal and tangential direction of the wood/bark interface on woody plant beech (Fagus sylvatica L.) during one year. The growing period and dormant period and moisture of the wood/bark interface proved to be important factors influencing the shear strength. The shear strength measured during the dormant period in the greenstate showed values approximately 100% higher than those measured during the growing period. Considering the 12%-moisture, the values of shear strength proved to be circa 300% higher in comparison to the green state. The shear area during the dormant period was led through the zone of the last-created sieve tubes of non-collapsed late phloem, whereas during the growing period the shear area passed through the cambium zone. The structure of shear areas is also significantly influenced by diverse structure of narrow and wide phloem rays.

WOOD RESEARCH Volume 64, Number 5, 2019
Tatiana Vilkovská, Ivan Klement, and Igor Čunderlík

Longitudinal contraction of reaction and opposite wood during drying process

Reaction beech wood has different anatomical and also chemical characteristics than normal (opposite) wood. The difference in density is conditioned by percentage of G–layer. Fibers cells in reaction beech wood have a different cell wall structure and a different chemical composition, as well. Longitudinal contraction was noticeable in reaction (tension) samples, where it was several times higher, what could be expected considering the physical properties of reaction beech wood. Our measurements confirmed that drying time has remarkable effect on longitudinal contraction. Higher longitudinal contraction was measured in temperature 60°C and 120°C, which had almost identical drying time. The issue of variability initial moistures did not affect the drying process and samples reached approximately equal final moisture content. Reaction beech wood is a very serious problem in nowadays wood production.